Fruit availability and human disturbance influence forest elephant group size

Social living provides benefits to group members, but these benefits come at a cost. In fissionefusion societies, individuals or small groups leave and join different groups as ecological constraints on group size fluctuate. Little research has been conducted on how human disturbance influences fission efusion groups after accounting for ecological conditions. As a large, wide-ranging species with large resource needs facing increasing human disturbance (e.g. poaching and habitat loss), African forest elephants, Loxodonta cyclotis, provide unique insight into how environmental, social and anthropogenic factors influence group size. We reconstructed forest elephant social groups using noninvasive genetic samples extracted from elephant dung collected while tracking GPS-collared forest elephants. Through a novel application of hierarchical markerecapture models, we estimated group size and the anthropogenic, demographic and environmental factors associated with fluctuations in group size. We found that high fruit availability was associated with a decrease in group size and that human disturbance (measured as an index of the global human footprint) was associated with an increase in group size, but to a lesser degree. Understanding social group dynamics is important for ensuring effective population management of forest elephants, both for tracking when large groups might be at risk from poaching and preventing the negative health associations of suboptimal group sizes such as increased stress and decreased reproduction. Additionally, our integration of genotyping, satellite remote sensing and statistical methods can inform the study of forest elephants and other cryptic species into the future. (c) 2023 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.